I only recollect one game in development that will support the new DX10 API with SM4.0 - so I don't know whether SM4.0 will be big this year. Current DX9.0 cards (X1900/7900) will run in the DX10 environment, but without SM4.0 (if it is at all going to be used games wise by Dec 2006).

As far as I've seen, it appears that all nVidia GeForce and all ATi Radeon cards will indeed actually be supported under Vista and DirectX10, but will largely all be "rated 1," at least for the ones without SM 2.0 support. None of them, it seems, have support for SM 4.0, though rumors persist of fragments of such support in The GeForce 7, and especially Radeon X1k cards, particularly given the latter's connection with the Xbox 360's Xenos GPU, which does clearly contain some things that could crop up in SM 4.0. However, they would not likely be worthwhile; better to wait for the GeForce 8 and Radeon X2k cards, which should clearly bring out DirectX10 support at the full level. Of course, it seems that said cards won't work outside of Windows Vista...

Don't you feel that both Nvidia and ATi would make mention of this fact? Just a question. If the 1900/7900 had such support, they will market it till the wheels come off. Somehow I feel that there is no definate spec for Vista at this stage with regards to what DX10 will be using in it's first round...